Some hydraulic systems include a positive flow control system by combining an electronically actuated valve, e.g., a closed center control valve, with an electronically actuated displacement control pump. A positive flow control system may maximize efficiency while eliminating the mechanical complexity associated with traditional load sensing systems. In one embodiment, a positive flow control system provides improved system response, in part, by providing control commands to the pump and valves that are proportional to the operators inputs. Improved system response may be provided if the desired pressure may be quickly provided to the system, via the pump and the valves, when it is requested. However, unless the movement of the valves is accurately timed to the pump displacement, pressure spikes in the system will result. For example, if the valves close before the pump destrokes, then the remaining pump flow has nowhere to go but over the relief valve, which has several undesirable effects including increasing the pump motor work load.
Some approaches to this problem have attempted to add time delays to the pump or valve commands to insure, for example, that the control valves open before the pump is stroked up while the implement was accelerating, and the pump destroked before the valves where closed while the implement was decelerating. The nonlinear nature of the time delays makes the approach of adding time delays an ineffective solution.
The present invention is directed to overcoming one or more of the problems identified above.